Resolve iCloud conflict versions before reads (last-writer-wins)

Ports QuickRabbit's resolveConflictsIfAny (R4.3) into the eviction-safe read
path: before every coordinated read, pick the NSFileVersion with the latest
modification date, promote it to the canonical file inside a coordinated
write, mark all conflicts resolved, and prune the losers. Without this,
conflict siblings from two-device edits (workout logs edited mid-session are
the risky case) accumulate silently and a read returns whichever version the
filesystem hands back.

Claude-Session: https://claude.ai/code/session_01SY5jsAUf4qoPxSvv8xAqXS

Workouts/Sync/ICloudFileManager.swift

@@ -34,11 +34,13 @@ actor ICloudFileManager {
         if let error = coordError ?? writeError { throw error }
     }
 
-    /// Eviction-safe read: materializes an evicted file (bounded wait) before the
-    /// coordinated read, so callers never decode a dataless placeholder. Throws on
-    /// download timeout rather than skipping — a silently dropped evicted file
-    /// looks to the user like the record was deleted.
+    /// Eviction-safe, conflict-safe read: resolves any iCloud conflict versions,
+    /// materializes an evicted file (bounded wait), then does the coordinated
+    /// read — so callers never decode a dataless placeholder or a stale conflict
+    /// sibling. Throws on download timeout rather than skipping — a silently
+    /// dropped evicted file looks to the user like the record was deleted.
     func read(relativePath: String) async throws -> Data {
+        resolveConflictsIfAny(at: documentsURL.appendingPathComponent(relativePath))
         try await ensureDownloaded(relativePath: relativePath)
         let fileURL = documentsURL.appendingPathComponent(relativePath)
         var coordError: NSError?
@@ -156,6 +158,52 @@ actor ICloudFileManager {
         return components.joined(separator: "/")
     }
 
+    // MARK: - Conflict resolution
+
+    /// If iCloud Drive created conflict versions (concurrent writes from
+    /// different devices), pick whichever has the latest modification date,
+    /// promote it to the canonical file, and mark every conflict resolved.
+    /// Whole-file last-writer-wins by mod-date — honest for one-file-per-record
+    /// data. Left unresolved, conflict siblings accumulate silently and a
+    /// coordinated read returns whichever version the filesystem hands back.
+    private func resolveConflictsIfAny(at fileURL: URL) {
+        let conflicts = NSFileVersion.unresolvedConflictVersionsOfItem(at: fileURL) ?? []
+        guard !conflicts.isEmpty else { return }
+
+        let currentDate = NSFileVersion.currentVersionOfItem(at: fileURL)?.modificationDate ?? .distantPast
+        var winnerDate = currentDate
+        var winnerVersion: NSFileVersion?
+
+        for version in conflicts {
+            if let date = version.modificationDate, date > winnerDate {
+                winnerDate = date
+                winnerVersion = version
+            }
+        }
+
+        // Promote the winner and prune the losers inside a coordinated write —
+        // these are real file mutations (replaceItem / removeOtherVersions) and
+        // must not race a concurrent write or the iCloud daemon; NSFileVersion
+        // does not coordinate internally.
+        var coordError: NSError?
+        NSFileCoordinator().coordinate(writingItemAt: fileURL, options: .forReplacing, error: &coordError) { url in
+            if let winner = winnerVersion {
+                do {
+                    try winner.replaceItem(at: url, options: [])
+                } catch {
+                    print("[Sync] Conflict promotion failed for \(url.lastPathComponent): \(error)")
+                }
+            }
+            for version in conflicts {
+                version.isResolved = true
+            }
+            try? NSFileVersion.removeOtherVersionsOfItem(at: url)
+        }
+        if let coordError {
+            print("[Sync] Conflict coordination failed for \(fileURL.lastPathComponent): \(coordError)")
+        }
+    }
+
     // MARK: - Eviction
 
     /// Triggers a download for an evicted file and polls until it materializes.